β-Cyclodextrin conjugated magnetic nanoparticles as a novel magnetic microvessel and phase transfer catalyst: synthesis and applications in nucleophilic substitution reaction of benzyl halides

This paper presents a feasible protocol for the preparation of β-cyclodextrin conjugated Fe₃O₄ magnetic nanoparticles as an efficient microvessel and host system for nucleophilic substitution reaction of benzyl halides in water. No evidence for the formation of by-product for example isothiocyanate or benzyl alcohol was observed and the products were obtained in pure form without further purification. The characteristics results of FT-IR, XRD, TGA and SEM shows that β-CD is grafted onto Fe₃O₄ nanoparticles. The nanomagnetic catalyst could be readily separated from solution via application of an external magnet, allowing straightforward recovery and reuse.     

Ultrafast Fluorescence Spectroscopy via Upconversion and Its Applications in Biophysics

In this review, the experimental set-up and functional characteristics of single-wavelength and broad-band femtosecond upconversion spectrophotofluorometers developed in our laboratory are described. We discuss applications of this technique to biophysical problems, such as ultrafast fluorescence quenching and solvation dynamics of tryptophan, peptides, proteins, reduced nicotinamide adenine dinucleotide (NADH), and nucleic acids. In the tryptophan dynamics field, especially for proteins, two types of solvation dynamics on different time scales have been well explored: ~1 ps for bulk water, and tens of picoseconds for “biological water”, a term that combines effects of water and macromolecule dynamics. In addition, some proteins also show quasi-static self-quenching (QSSQ) phenomena. Interestingly, in our more recent work, we also find that similar mixtures of quenching and solvation dynamics occur for the metabolic cofactor NADH. In this review, we add a brief overview of the emerging development of fluorescent RNA aptamers and their potential application to live cell imaging, while noting how ultrafast measurement may speed their optimization.     

基于液滴微流控接口的高效液相色谱-毛细管电泳二维分离平台初探

蛋白质组体系的高度复杂性需要更高分辨率的多维分离技术。近年兴起的液滴技术在微纳尺度样品操控方面具有微体积、低扩散、无返混等独特优势,有望为多维分离平台的接口提供解决方案。通过采用不同结构的液滴微流控芯片可以实现“液滴生成”与“油相排除”功能,进行样品由连续流-非连续流-连续流的高效转移,将不同的分离模式进行二维耦联。本研究利用液滴作为接口技术耦联高效液相色谱与毛细管电泳构建二维分离系统,以蛋白质降解的复杂多肽混合物为样品,考察了液滴接口二维分离平台的可行性和有效性,并获得3000以上的峰容量,初步展示了该接口技术在多维分离分析领域的应用潜力。     

Generation of grid multi-scroll chaotic attractors via switching piecewise linear controller

In this Letter, a novel method is developed for generating grid multi-scroll chaotic attractors using switching piecewise linear controller. First, a third-order linear system is designed to ensure that its unique equilibrium point belongs to a saddle-focus type with index 2 and the corresponding eigenvalues satisfy Shilnikov conditions. Then, by three different types of switching control strategies, the equilibrium point can be extended along both xy plane and z axis direction, so as to generate grid multi-scroll chaotic attractors. The dynamical behaviors are further analyzed. Moreover, an improved module-based circuit is designed for realizing 5×3 and 4×4 grid scroll chaotic attractors, and the experimental results are also obtained, which is consistent with the numerical simulations.     

Cucurbit[10]uril

Melamine diamine 1 is able to displace CB[5] from the CB[10].CB[5] complex resulting in CB[10].12 and precipitated CB[5].1. We were able to isolate free CB[10] by treatment of CB[10].1 with acetic anhydride followed by washing with MeOH, DMSO, and water. The spacious cavity of CB[10] is able to complex large guests, including a cationic calix[4]arene derivative in its 1,3-alternate form (CB[10].1,3-alt-3). The addition of adamantane carboxylic acid (4) to CB[10].3 triggers a conformational change during the formation of termolecular complex CB[10].cone-3.4.     

“受阻路易斯酸碱对”催化的2,3-二取代2H-1,4-苯并噁嗪氢化反应机理研究

在受阻路易斯酸碱对（FLPs）催化的2，3-二取代2H-1，4-苯并噁嗪氢化反应中，3号位取代基不同会导致反应效率极大改变，因此我们选取反应活性具有较大差别的三种底物作为模型化合物对其反应机理进行了研究，建立了氢化反应势能面.发现当B（C₆F₅）₃与2，3-二苯基2H-1，4-苯并噁嗪或2-甲基-3-苯基2H-1，4-苯并噁嗪混合后，会形成FLPs与路易斯酸碱加合物的混合物.而将B（C₆F₅）₃与2，3-二甲基2H-1，4-苯并噁嗪混合后主要形成没有催化活性的路易斯酸碱加合物，因其能量低于FLPs，在催化体系中不容易转化为FLPs，这导致三种模型化合物在FLPs催化的氢化反应中效率不同.进一步的取代基电子效应及位阻效应计算表明：B（C₆F₅）₃与2-甲基-3-取代2H-1，4-苯并噁嗪混合后形成的路易斯酸碱加合物和FLPs化合物之间稳定性差别源于3位取代基空间位阻不同.     

单原子催化剂的制备、表征及催化性能

单原子催化剂(SACs)是指金属以单原子形式均匀分散在载体上形成的具有优异催化性能的催化剂.与传统载体型催化剂相比,SACs具有活性高、选择性好及贵金属利用率高等优点,在氧化反应、加氢反应、水煤气变换、光催化制氢以及电化学催化等领域都具有广泛应用,是目前催化领域的研究热点之一.常见的SACs制备方法有共沉淀法、浸渍法、置换反应法、原子层沉积法以及反奥斯瓦尔德熟化法等.实验及理论研究表明,单原子催化剂高的活性和选择性可归因于活性金属原子和载体之间的相互作用及由此引起的电子结构改变.载体是影响单原子催化剂性能的重要因素之一.目前常用的SACs载体有金属氧化物、二维材料和金属纳米团簇等,本文着重综述了这三种负载型SACs的制备、表征、催化性能及催化机理,并概述了SACs未来可能的发展方向和应用.研究表明,共沉淀法、湿浸渍法和反奥斯瓦尔德熟化法等方法可用来制备氧化物负载的SACs.高角环形暗场像-扫描透射电子显微镜(HAADF-STEM)表明金属是以单原子形式均匀分散在载体上,近边X射线吸收精细结构(XANES)结果表明金属原子与载体之间存在着强相互作用.实验和理论研究均表明该类催化剂在CO氧化反应、水煤气转化及乙炔加氢生成乙烯等反应中具有高的催化活性和稳定性.采用化学气相沉积法和原子层沉积法等方法可以将金属原子稳定地负载在具有缺陷活性位点的石墨烯、MXene及六方氮化硼等二维材料上并相应制备出SACs.X射线吸收精细结构谱(EXAFS)和XANES分析表明样品中金属以单原子形式存在,而且金属原子与载体之间也存在着强相互作用,理论计算表明金属原子与二维载体之间的电荷转移是SACs活性高的主要原因.置换反应法和连续还原法是制备溶胶型SACs的有效方法,其中置换反应法可将活性金属原子原位组装在金属模板团簇的顶点位置,连续还原法可将活性原子负载于金属模板团簇的表面.DFT计算表明活性原子和金属模板团簇之间存在电荷转移效应,这是溶胶型SACs具有非常高的催化活性的主要原因.SACs下一步的研究方向可能是:(1)研究开发新型SACs,尽可能提高催化剂中活性金属原子的含量;(2)深入研究SACs的结构、活性以及催化机理之间的关系;(3)尝试将SACs大规模应用于工业催化.     

结晶聚合物的辐射效应：多官能团单体对LDPE的结晶成核作用

根据x射线、电镜、DSC和凝胶分数的测试结果,讨论了多官能团单体结构对低密度聚乙烯聚集态结构的影响以及结晶度与辐射交联(或剂量)的关系。发现由于单体的存在导致低密度聚乙烯结晶度增加而结晶尺寸变小(即结晶成核效应);成核效应越大,增强辐射交联的效果也越大。添加具有高结晶成核作用的单体有利于低密度聚乙烯的辐射交联,同时也加速其结晶结构的破坏。     

Dual-wavelength nonvolatile holographic storage

A simple, convenient and effective way is demonstrated to reduce the field losses of the reconstructed image in the dual-wavelength nonvolatile holographic storage by adding a cylindrical lens in the holographic recording configuration. The experimental results show that this technique makes the dual-wavelength nonvolatile holographic storage compact and practical.     

Hausdorff dimension of Cantor attractors in one-dimensional dynamics

In this paper, we study the Hausdorff dimension of Cantor attractors of smooth interval maps with non-flat critical points. We prove that the Hausdorff dimension is bounded from above by a constant less than 1 which depends only on the number and order of the critical points.